Thursday, July 11, 2013

Paper finds the Alps were nearly ice-free 2000 years ago during the Roman Warming Period

The Alps were largely ice-free 2000 years ago during the Roman Warming Period, demonstrated by wood finds in today's glacial alpine regions by Dr. Christian Schlüchter. Dr. Schlüchter is Professor of Quaternary and Environmental Geology at the University of Bern, and lecturer at ETH Zurich.

Dr. Schlüchter investigated high flood deposits of a glacial river in the immediate foreland of the Lower Bernese Oberland and found 30 to 60 centimeters thick pieces of wood and remnants of a moor. Tree remains were associated with a Arvenstamm (alpine conifer) and dated to 4,920 ± 60 years before present. The Moor remains dated to 2,100 ± 50 years before present. The finds are extraordinary, especially since trees and a marsh occur only at locations where no permanent ice is present and the tree line that was significantly higher than today. The previous datings revealed that in the last 10,000 years, slightly more than 50% of the time the glaciers were significantly shorter than today.

Prof. Schlüchter: "Between 1900 and 2300 years ago the lower tips of the glaciers lay at least 300 metres higher than today. At the time of the Romans they would hardly have been recognised as glaciers for the simple reason that their lower reaches lay above the Alpine passes that were used at the time and would not have been an obstacle.“ This would also explain why, in the otherwise very detailed accounts, the Roman chronicles contain hardly any mention of glaciers. When Hannibal in 218 BC with his war elephants (in winter!) crossed the Alps and invaded the Roman heartland, the alpine passes were largely ice-free. This was the time of the Roman climate optimum. Fig. 2 left below shows how it looked there after reconstruction at that time. Schlüchter says, "These findings call for a fundamental revision of the prevalent view of a relatively strong coverage of the Alps with glaciers since the ice age. Because for long periods the Alps were greener than they are today."Martin Funk (5), Professor for Glaciology at the Laboratory of Hydraulics, Hydrology and Glaciology (VAW), looked at Schlüchter's results. "I see no reason to doubt the results and the conclusions overall, at the most a few details,“ he said.

Fig.2 left shows the Susten Pass (pass 2,224 above sea level), as it looked about 2,000 years ago in Roman times, according to the investigations of Dr. Schlüchter. The Steigletscher has withdrawn to the level of Tierberglihütte (2,795 m), and the tree line was significantly higher than today. The right figure shows the glacier around 1993 and its extension in 1856 (after the "Little Ice Age") and in 1922.